Prognostic value of rhodamine-efflux and MDR-1/P-170 expression in childhood acute leukemia.

The evidence that mechanisms other than P-170 expression may influence its "pump" and the retention/efflux of chemotherapeutic agents, prompted us to investigate the value of a functional multidrug resistance (MDR) assay in a series of childhood acute leukemia samples. Forty acute leukemia cases, mainly of lymphoid origin (ALL), were evaluated for MDR expression using a functional test based on rhodamine-123 efflux (Rhd-E). This was correlated with the quantification of P-170 external epitopes based on the positivity with the 4E3.